Consumer safety concerns are mounting as engineered nanoparticles (ENPs) are increasingly being incorporated into consumable products, such as food, drugs, and personal care products. While toxicological effects of inhaled and skin-contacting ENPs have been evaluated, very little is known about the short-term and long-term effects of ingested ENPs. To evaluate the safety and possible toxic effects of ENPs on the gastrointestinal (GI) epithelium, human primary cell-based screening assays are urgently needed. Specifically, using more complex, immunocompetent in vitro systems that mimic the native tissue microenvironment would greatly advance our ability to accurately assess the intestinal toxicity of ingested ENPs. The overall objective of this proposal is to develop an in vitro test methodology that accurately determines the toxicological profile of ENPs following intestinal exposure. To achieve this goal, we will utilize MatTek Corporation?s highly differentiated, organotypic EpiIntestinal tissue model containing epithelial cells, fibroblasts, and immune cells. During Phase 1, a prediction model will be developed to identify ENPs that are likely to cause gastrointestinal (GI) irritation, inflammation or genotoxicity, or perturb homeostasis (barrier function) in the GI tract. Since repeat exposure to ENPs is implicated in nanotoxicity, both acute and chronic exposure conditions will be simulated. Such a human cell-based, in vitro GI toxicity model which recapitulates the human small intestine will have enormous market utility for screening ingestible nanomaterials used in the pharmaceutical and food industries.